Railway car retarder control systems



p 1967 E. o. GARRETT, JR ETAL RALLWAY CAR RETARDER CONTROL SYSTEMS 2Sheets-$heet 1 Filed June 24, 1966 1H1 H i I NIH 7 0 (1011/1 06 /1 0nmwfa:5.

p 1967 E. o. GARRETT, JR ETAL 3,340,963

RAILWAY CAR RETARDER CONTROL SYSTEMS Filed June 24, 1966 2 Sheets-SheetI l [V V I; IV @7035 2! Edward 0. (,Qufle J1. and J BY Pezjen v M/VoblaUnited States Patent 3,340,963 RAILWAY CAR RETARDER CONTROL SYSTEMSEdward 0. Garrett, Jr., Penn Hills Township, Allegheny County, and PeterM. Noble, Valencia, Pa., assignors to Westinghouse Air Brake Company,Swissvale, Pa., a corporation of Pennsylvania Filed June 24, 1966, Ser.No. 560,178 15 Claims. (Cl. 188-62) Our invention relates to railway carretarder control systems and more particularly to hydraulically-actuatedpneumatically-powered electrically-controlled systems for weightproportional car retarders which may be rapidly and selectivelyconditioned to assume either a braking or a non-braking position,

It has been found that an inert car retarder when equipped with anappropriate control system is ideally suited for group and hump carretarder operations in classification yards since this type of retarderapplies a braking force which is directly proportional to the respectiveWeight of the car under retardation and therefore removes approximatelythe same velocity head from all cars irrespective of their weight. Whilevarious types of weight proportional car retarders and control systemsfor such reta-rders have been previously proposed, it is noted thatthese previous proposals lack certain essential requirements andnecessary characteristics which limited the use of such retarderarrangements. For example, many of the previous weight proportional carretarder arrangements were preferably employed at the end of the classtracks in a classification yard for simply stopping and holding thefirst car entering the respective class track in lieu of track skates.Accordingly, the control system for such a skate retarder was mainlyemployed for the purpose of extending the life of the brake shoes of theretarder when the classed cars were pulled from the class track by alocomotive. That is, it was common practice to utilize an open-type ofhydraulic releasing system which would permit the opening of the carretarder so that the cars could be easily removed from the class trackwithout excessive wear on the braking surfaces of the brake shoes. Sucha hydraulic releasing system normally included a suitable controlledcylinder and piston properly positioned beneath the running rail orunder the levers of the operating units of the car retarder foreffecting the opening of the brake shoes. While the use of such ahydraulically controlled weight proportional car retarder arrangement isquite satisfactory at the exit end of class tracks, its use in a groupor a hump retarder application is generally not acceptable due to theinherent slow or sluggish operation and the intrinsic leakage problemsassociated therewith. That is, the speed with which an open hydrauliccontrol system moves the car retarder between its non-braking andbraking positions is limited and generally too slow for high speedrepetitive acting retarder operations, such as, demanded by group andhump retarder installations. Similarly, since the apparatus of hydrauliccontrol system is quite extensive and normally includes hydraulic pumps,reservoirs, valves, stop-cocks, pressure switches, and extensive piping,it is constantly susceptible to loss of liquid and to drop in pressuredue to leaks. While several attempts have been made to utilize such carretarders and open hydraulic systems in group and hump applications, theresults were generally unsatisfactory in that once the retarder wasreleased during car retardation it could not be elfectively reactivatedto its normal braking position for the same car. It is obvious that inorder to achieve effective braking and control of the car passingthrough the retarder, the retarder must be capable of reclosing at leastbetween the trucks of the car so that 3,340,963 Patented Sept. 12, 1967the braking effort may be reapplied in case the speed of the carincreases above the preselected given speed. While it would appearobvious to simply increase the pressure of the hydraulic control systemsuch an expedient is generally objectionable in that the leakage problemis proportionally increased with greater pressures, and thereforeimproved operation is only obtained with increased cost and decreasedeffectiveness. Accordingly, the complexity and expensiveness of theseformer open hydraulic control systems are not only physicallyprohibitive but also economically unjustifiable in terms of reliable andeflicient operation.

Accordingly, it is an object of the present invention to provide animproved control system for a car retarder which has universalapplication.

A further object of our invention is to provide a hydraulically-actuatedpneumatically-powered electricallycontrolled systems for weightproportional car retarders.

Another object of our invention is to provide a unique system forcontrolling weight proportional retarders which may be employed in groupand hump applications as well as used in place of track skates.

Still another object of our invention is to provide an improved lowpressure control system having a short response time so that a carretarder may be quickly moved from its non-braking position to itsbraking position for achieving repetitive braking action on a railwaycar.

Yet another object of our invention is to provide new and improvedWeight proportional car retarder control system which renders andretains the car retarder ineffective in retarding a car when moved toits non-braking position.

Still yet another object of our invention is to provide a uniquepneumatic-hydraulic-electiic control system for a car retarder withgreater security in that a hydraulic leak does not adversely alTect thegeneral operation and elfectiveness of the entire car retarder.

Yet a further object of our invention is to provide a uniquepneumatic-hydraulic-electric control system for a car retarder whichassumes and/or maintains its braking position for positively stoppingrailway vehicles during periods of electrical power failures.

Still yet a further object of our invention is to provide an improvedcar retarder control system which is simple in design, economical tomanufacture, endurable in use, and eflicient and reliable in operation.

Briefly, our invention relates to pneumatically-poweredhydraulically-actuated electrically-controlled systems for a weightproportional car retarder which may be conditioned either to retard avehicle in accordance with its weight or to permit the free passage of avehicle. The car retarder is of the friction wheel engaging type andpreferably includes a plurality of operating units each having a pair ofsupporting levers positioned on opposite sides of the running raiL'Theinner lever of each operating unit is pivoted about a point having afixed height while the other lever of each operating unit is pivotedabout a point having a variable height. The height of the variable pivotpoint of each outer lever is controlled by individual hydraulic ramswhich when fully extended cause the retarder to assume its braking orclosed position and which when fully contracted cause the retarder toassume its non-braking or open position. The hydraulic rams form part ofa closed-type of hydraulic circuit which is under the control of anopen-type of pneumatic circuit. The hydraulic and pneumatic circuitsinclude solenoid control valves which when deenergized complete aunidirectional communication path from a source of pneumatic pressure tothe hydraulic rams for placing the retarder in its braking position. Onthe other hand, when the solenoid control valves are energized abidirectional com- 3 munication path is completed between the hydraulicrams and atmosphere thereby allowing the retarder to assume itsnon-braking position. The retarder remains in its nonbraking positionuntil the source of pneumatic pressure is again applied to the pneumaticcontrol circuit.

In the first embodiment, the pneumatic control system and the hydrauliccontrolled circuits are interconnected by a plurality of individualpneumatic-hydraulic transducers.

I In the second embodiment the pneumatic control circuit isinterconnected to the hydraulically-controlled circuit by a singlepneumatic-hydraulic transducer.

The above objects and other attendent features and advantages of thisinvention will become more fully evident from the following detaileddescription when considered in connection with the accompanying drawingswherein:

FIG. 1 is a diagrammatic view of one form of a control system for aweight proportional car retarder embodying the present invention.

FIG. 2 is a diagrammatic view of a modified form of a control systemembodying the present invention showing a sectionalized end view of theweight proportional car retarder of the type preferably employed in ourinvention.

Referring to the drawings wherein like parts are indicated by likereference numerals, and in particular to FIG. 2, there is shown asectionalized elevational view of the weight proportional car retarderin its braking position and specifically the details of an operatingunit OU. While the control system is illustrated as being capable ofcontrolling a five-unit group or hump car retarder, it is understoodthat the system may be designed and constructed to accommodate a greateror lesser number of retarder operating units, as desired. It has beenfound that only five operating units are required for a car retarderhaving a length of approximately sixteen feet (16) for effectively andefliciently handling even the heaviest railway car in use at the presenttime. As will be described hereinafter the particular retarder length ischosen as such that the retarder may be reset between the trucks of eventhe shortest railway vehicle in commercial existence. As shown in FIG.2, the reference character 1 designates one track rail of a stretch ofrailway track over which the wheels of railway vehicles pass. The rail 1is supported by the operating units U each of which consists of a pairof substantially identical levers 2A and 2B disposed laterally onopposite sides of the rail 1. The inside bottom portions of the leversare securely held in suitable relationship by means of a through-typetie bolt 3. As shown, the upper surface of the inside bottom portion ofthe levers engages the flange of the rail 1 while the bottom surface ofthe inside bottom portion normally rests on a thrust or hearing platenot characterized, suitably mounted on cross tie 4, when the carretarder is in its braking position and no vehicle is being retarded orwhen the car retarder is in its non-braking position. The inside topportion of each lever has secured thereto in any suitable manner, thebraking elements of the car retarder. These braking elements may consistof braking rails or as shown brake beams 5 and brake shoes 6 which areadapted to frictionally engage the opposite sides of the car wheels whenthe retarder is in its braking position. The underside of the outsideend of lever 2B is shown pivotally mounted on a suitable supportingmember 7. The supporting member 7 has a predetermined height and issuitably secured by means of, for example, a tie plate which may besuitably mounted on the cross tie 4. The outside end of lever 2A of eachoperating unit 0U is suitably connected to a vertically movable pistonor plunger 10 of a hydraulic ram R which when fully extended, as shown,has a height substantially equal to that of support 7. The piston isshown interconnected to the outside end of lever 2A by means of aneye-bolt type of mechanical link 11; however. it is understood that anysuitable mechanical interconnection may be employed which will allowpivotal movement therebetween. As shown, the cylinder 12 of eachhydraulic ram R is also suitably secured to and supported by the crosstic 4.

Referring now to FIG. 1, wherein the details of the operating units 0Uhave been excluded for the sake of convenience, there is shown one formof a retarder control system for a five-unit weight proportional carretarder. The control system of FIG. 1 is illustrated as consisting of aplurality of independent closed hydraulic controlled circuitscooperatively associated with the car retarder operating units, seeuppermost ram R and lever 2A, and an open pneumatic control circuit.

The closed hydraulic circuits comprised within the blocks 20 may be ofthe type shown and described in our copending application for LettersPatent of the United States, Ser. No. 618,417, filed Feb. 24, 1967, forRailway Braking Apparatus. As shown, each hydraulic circuit comprises apackaged unit including a separate hydraulic ram R, a solenoid controlvalve designated generally at 21, and a pneumatic-hydraulic transducer26. The control .valves may be of the internally piloted poppet two-waytwo-position spool type which allows bidirectional flow when solenoid 22is energized and which only permits unidirectional flow when solenoid 22is deenergized. That is, each valve 21 is provided with a check valve 23which only permits fluid to flow from the transducer 26 to the hydraulicram R. Each valve 21 also includes a biasing spring 24 for urging thevalve to its unidirectional flow position. As shown, the input side ofeach valve 21 is coupled by suitable conduit to the hydraulic side ofthe separate pneumatic-hydraulic transducers 26 while the output side ofeach valve 21 is coupled by conduit to a separate hydraulic ram R.

As shown, the pneumatic control circuit comprises a suitably regulatedmotor-driven compressor 30 pneumatically communicating and feedingreservoir or tank 31 which form a low pressure supply, such as, p.s.i.source. The output from reservoir 31 is connected by conduit to theinput port of a solenoid control valve 32. The control valve 32 ispreferably a two-way two-position spool valve which includes operatingsolenoid 33 and return spring 34. When solenoid 33 is deenergized, afluid communication path is established from reservoir 31 through valve32 to conduit manifolded together, and designated generally at 35, whichin turn is interconnected to the pneumatic-side of each of thepneumatic-hydraulic transducers 26. On the other hand, when the solenoid33 is energized, the valve 32 is shifted so that the output fromreservoir 31 becomes blocked and the manifold 35 and, in turn, thepneumatic side of transducers 26 are vented, for example, to atmosphere.

Each of the solenoids 22 of valve 21 are electrically connected inparallel by conductors 40 which in turn are connected to the controlapparatus by suitable leads 41. Similarly, the solenoid 33 is connectedto the control apparatus by means of suitable conductors 42. The controlapparatus which may be operated manually under visual observance of anoperator or automatically under supervision of a programmed computer ispreferably remotely situated at a suitably located control oflice.

In describing the operation of the retarder control system, it will beinitially assumed that a railway vehicle or car is approaching theretarder at a speed in excess of a predetermined computed speed which isnormally necessary for it to safely couple with a preceding vehicle inits destined class track. Therefore, it is desirous that the retarder bemoved in its braking position, in the manner illustrated in FIG. 1, sothat the brake shoes 5 may frictionally engage the opposite sides of thevehicle wheels for reducing the speed of the fast approaching railwayvehicle. As previously mentioned, the brake shoes will close and theretarder will move to its braking position by raising the pistons 10 ofthe hydraulic rams R to their fully extended positions. The hydraulicrams R are extended, as shown in the drawings, when solenoid 33 of thepneumatic control valve 32 and the solenoid 22 of the hydraulic controlvalve are deenergized. With the solenoid 33 deenergized, a pneumaticflow path is established from the reservoir 31 through the pneumaticvalve 32 to the input of manifold 35 and in turn to the pneumatic sideof each of the transducers 26. With the solenoids 22 of the hydraulicvalves 21 deenergized a unidirectional fluid path is established fromthe hydraulic side of transducers 26 to the hydraulic rams R. Thepressurization by the 100 p.s.i. source on the pneumatic side of thetransducers 26 is transmitted to the hydraulic side of transducers 26 sothat the fluid flows through check valve 23 to the hydraulic rams R.Accordingly, the pistons are rapidly forced toward their fully extendedpositions. The 100 p.s.i. source of pressure is relatively low but is ofsuflicient magnitude to displace pistons 10 of the hydraulic rams R andlift the levers 2A and in turn the entire retarder to its brakingposition. When the pistons 10 of rarns R reach their fully extendedpositions, the solenoid 33 is energized and valve 32 is shifted so thatmanifold 35 and the pneumatic-side of transducers are vented toatmosphere, the purpose of which will be described hereinafter. Theshifting of valve 32 also causes the output from reservoir 31 to becomeclosed so that the motor and compressor need not be operatedunnecessarily.

It is noted that once the hydraulic rams R have been fully extended, theventing of the pneumatic circuit by the energization of the solenoid 32of pneumatic valve 33 does not materially affect the closed hydraulicsystem and the retarder remains in its braking position. That is, eventhough the pneumatic-sides of transducers 26 are now at atmosphericpressure, the check valves 23 prevent reverse fluid flow from thehydraulic rams R so that the retarder is locked in its braking position.Accordingly, as the front Wheel of the first truck of the railwayvehicle enters the retarder, the levers 2A and 2B of the operating unitsOU pivot about their respective support 6 and the hydraulic ram R. Thepivoting action of the levers about their outer extremity causes alifting of the rail 1 and the vehicle along with a clamping or brakingaction on the sides of the vehicle wheel by the brake shoes 5 inproportion to the weight of the railway vehicle. This braking action onthe wheels and retardation of the vehicle continues until it isdetermined, assuming automatic operation, by suitable speed measuringmeans, such as radar, that the speed of the vehicle has reached apreselected computed value. When the speed of the vehicle reaches thispreselected value, it is desirous to quickly release the retarder sothat the speed of the vehicle is not reduced below the speed necessaryfor the vehicle to reach its destination and couple with the precedingvehicle in its respective class track. Accordingly, it is advantageousto have as short as possible release response time in order toefliciently and accurately control the velocity of railway cars. Torelease the retarder it is simply necessary to energize the solenoids 22of the hydraulic valves 21 so that the spool establishes'a fluidcommunication path from the hydraulic rams R to the transducers 26. Thatis, when the solenoid control valve 21 is moved upwardly as viewed inFIG. 1 by the energization of solenoids 22, a bidirectional flow path isestablished between the hydraulic rams R and transducers 26. Thisunlocks the hydraulic fluid trapped in rams R so that the weight of thevehicle and retarder causes the hydraulic fluid in the rams R to berapidly transferred through the valves 21 to the hydraulic side of thevented transducers 26. The downward displacement of piston 10 causes thebrake shoes 5 to open wider than the width of the Wheels of the railwayvehicle so that the railway vehicle now may pass freely through theretarder. In actual practice it has been found that the car retarderwill move from its braking to its non-braking position in approximatelyone-third A) of a second. It is noted that the hydraulic rams R willremain in their compressed position and the brake shoes 5 will stay openeven after the departure of the wheels of the first truck of the vehiclefrom the retarder since the hydraulic circuit remains in a state ofequilibrium and the weight of the retarder alone is sufficient forholding the pistons 10 depressed. That is, the retarder remains in itsnon-braking position until such time as it is again desirous to operateand move the retarder to its braking position. It is readily apparentthat after the pistons 10 are fully depressed the solenoids 22 of thehydraulic valves may be deenergized and the retarder will still remainin its non-braking position. Accordingly, it is simply necessary tomomentarily energize solenoids 22 since the hydraulic rams will be fullycompressed in approximately /3 of a second, and therefore the powerrequirement is minimized due to the pulse energization of the solenoids.

As previously mentioned, the overall length of the retarder is less thanthe distance between the adjacent trucks of a railway vehicle so thatthe retarder may effect a braking action on the wheels of the secondtruck of the same vehicle. That is, if the speed of the vehicleincreases while passing through the retarder, it is necessary to againclose the retarder and reduce the speed of the vehicle to thepreselected value. Let us assume that the retarder has been released inthe manner as described above and that the speed of the vehicle hasrisen above the preselected value so that it is desirable to reclose theretarder. With solenoids 22 deenergized, it is simply necessary todeenergize solenoid 33 of the pneumatic valve 32 to again pressurize thepneumatic-side of transducers 26. Under such a condition the controlsystem is made ready and upon departure of the second wheel of the firsttruck from the retarder, the rams R are rapidly forced upwardly to theirfully extended positions and the retarder again assumes its brakingposition. In actual practice it has been found that the control systemwill displace the pistons 10 to their fully extended position or, inother words, the retarder will be moved from its non-braking to itsbraking position in less than 0.5 second. It has been found that with aresponse time of 0.5 second in moving the retarder between itsnon-braking to its braking position, the retarder may be reclosed andelfect braking on vehicles moving at a speed in excess of 15 miles perhour. When the rams reach their fully extended position, thesolenoid 33of the pneumatic valve may be energized so that the transducers 26 areagain vented to atmosphere and the retarder is again ready for effectinga braking action on the wheels of the second truck, the same asdescribed for the wheels of the first truck. When the speed of thevehicle is reduced to its preselected value, the retarder may be againopened or released simply by pulse energizing the solenoids 22 of thehydraulic control valves 21 so that the retarder will move to itsnon-braking position, in the manner as described above. Accordingly, theamount of retardation applied to any particular railway vehicles iseffectively controlled in accordance with the characteristics of thevehicle under retardation and therefore the leaving speed of the vehiclemay be accurately controlled.

Now if the speed of an approaching railway vehicle is at or below itspreselected computed value, and the retarder and control system are intheir respective non braking positions, no control action is taken andthe railway vehicle is permitted to pass freely through the retarder.However, if the retarder arrangement is in its braking position and thespeed of an approaching vehicle is at or below its preselected computedvalue, it is necessary to exercise a controlling action to open theretarder. Under this condition the solenoids 22 are simply energized sothat the fluid in rams R is unlocked. This allows the pistons 10 todecend and as the vehicle enters the retarder the weight of the frontwheel quickly forces the levers and brake shoes to open. Accordingly,the retarder promptly assumes its non-braking position so that only aslight dragging effect is exerted on the front wheel of the first truckand no retarding action is applied to the following wheels of therailway vehicle.

The fast release or snapopen action of the car retarder is the result ofutilizing a closed-hydraulic controlled circuit in combination with anopen-pneumatic control circuit. Generally speaking, this uniquecombination provides an instantaneous responsive type of retardercontrol which alleviates the long time delays and slow operation thatare normally inherent in the prior art type of open-type of hydrauliccontrol systems. In addition, by employing an open-type of pneumaticsystem for powering and closing the car retarder, the actuating time isminimized. That is, since an open-type of pneumatic system is muchfaster acting than an open-type of hydraulic system, the car retardermay be moved from its non-braking to its braking position in a shorterperiod of time than was heretofore possible.

It should be noted that the present retarder control system requiresonly a relatively low pressure source so that the major portion of theconduit and particularly the field piping is generally less susceptibleto leakage problems. A further advantage in utilizing apneumatic-powered hydraulic-actuated control system resides in the factthat a dual-line network is not necessary since the pneumatic circuitmay be directly vented to the atmosphere. Further, in reviewing FIG. 1,it is readily noted that only a small portion of the hydraulic controlcircuit is susceptible to high pressures, namely, the rams R and theconduit that leads to the output side of valves 21, and only during theretardation of the railway vehicles. An additional advantageous featureof our system is that of utilizing a plurality of individual closedhydraulic circuits, a failure of any one hydraulic circuit will notresult in total system failure. That is, the remaining hydrauliccircuits will supplement each other so that the retarder will functionproperly for eflectively reducing the speed of the railway vehicle.Accordingly, a failure of any hydraulic unit does not materially affectthe braking operation of the car retarder. Further, the system isfail-safe from an electrical standpoint in that it will assume and/ orremain in its braking position to retard and positively stop a railwayvehicle. For example, let us assume that the retarder is in its brakingposition when an electrical power failure occurs. The loss of powersimply allows the return spring 34 to shift the hydraulic valve 32. Thisdoes not materially affect the retarder and its control system since thefluid within the rams R remains trapped and the retarder is held in itsbraking position. Now, if power failure should occur when the retarderis in its non-braking position, the springs 24 quickly urge thehydraulic valves 21 to their undirectional fluid flow positions whilespring 34 quickly returns the pneumatic valve 32 to its power position.The pressure within reservoir 31 is suflicient to quickly and fullyextend the pistons 10 of the hydraulic rams R so that the retarderassumes its braking position in which position it is positively lockeddue to the deenergization of solenoids 22 of valves 21. Accordingly, thehighest degree of safety and security is achieved by the present controlsystem and a chance of physical injury and damage to personnel andproperty due to a run-away car is minimized.

Referring now to FIG. 2, there is shown a modified version of a retardercontrol system in accordance with the present invention. In the controlsystem of FIG. 2 the individual hydraulic rams R are fed from a singlepneumatic-hydraulic transducer 26. The hydraulic side of the transducer26' is interconnected by manifold 35 to the individual hydraulic valves21. However, in FIG. 2, the pneumatic side of transducer 26 is directlyconnected to the pneumatic valve 32 by a single conduit rather thanbeing manifolded as in FIG. 1. It is understood that the transducer 26'may be of the same general type as transducers 26 with the exceptionthat the volume of transducers 26' is greater than, and in the case athand, approximately five (5) times as great as,

8 the volume of transducers 26. It is noted that the operation of thecontrol system of FIG. 2 is the same as that of FIG. 1 so that the rapidclosing feature and snapopen releasing action are also inherentcharacteristics of this latter version. Like in FIG. 1, the retardercontrol system of FIG. 2 is shown in its brake actuating positionwherein the retarder is being moved to its braking position.Accordingly, solenoid 33 is deenergized so that pneumatic valve 32 iseffective in establishing a fluid communication path between thereservoir 31 and the pneumatic-side of transducer 26. As in FIG. 1, thepressurization of the transducer 26' causes the hydraulic field to bedisplaced from the hydraulic side of transducer 26' through the checkvalve 23 and in turn to the cylinders 12 of the hydraulic rams R. Thisfluid displacement causes the pistons 10 to be moved upwardly towardtheir fully extended position. When the hydraulic rams R become fullyextended and the retarder occupies its braking position, the solenoid 33is energized so that the transducer 26' is vented to atmosphere. Torelease and unlock the retarder it is simply necessary to energizesolenoids 22 so that fluid communication paths are established from thehydraulic rams R to the transducer 26. The retarder moves from itsbraking position to its non-braking position in a snap-open fashionunder the influence of the vehicle weight to quickly allow free passageof the railway vehicle. As in FLIG. l, the control system may berepetitively operated to reapply retardation to the same vehicle incases where the vehicle accelerates while passing through the retarder.Similarly, the retarder may be rendered ineffective in the same manneras described in FIG. 1 when retardation on a vehicle is not desired.

While the control systems and the carretarder have been described inrelation to group or hump operations, it is readily apparent that theretarder apparatus may be employed at the end of a class track forstopping and holding the first vehicle entering it, and when desired theretarder may be opened to permit the free and unimpelled withdrawal ofthe railway vehicles from the class track. Accordingly, we havedescribed a Weight proportional car retarder and particularly animproved control system having universal application in a classificationyard.

It will also be appreciated that while our invention finds particularutility in classification yards and in particular to hump and groupretarder operations, it is readily evident that the invention is notmerely limited thereto but may be employed in other environments, suchas car dumper applications. But regardless of the manner in which theinvention is used, it is understood that various alterations may be madeby persons skilled in the art without departing from the spirit andscope of this invention. It will also be apparent that othermodifications and changes can be made in the present described inventionand therefore it is understood that all changes, equivalents, andmodifications within this spirit and scope of the present invention arehere meant to be included in the appended claims.

Having thus described our invention, what we claim is:

1. A system for controlling the position of a car retarder comprising:hydraulic actuating means cooperatively associated with the carretarder, hydraulic circuit means fluidly coupled to said hydraulicactuating means, and pneumatic circuit means interconnected to saidhydraulic circuit means and having a source of pressure for causing thecar retarder to assume a first position when fluid is permitted to flowthrough said hydraulic circuit means in one direction and for enablingthe car retarder to assume a second position when fluid is permitted toflow through said hydraulic circuit means in the other direction.

2. A system as defined in claim 1 wherein said hydraulic actuating meanscomprises a ram.

'3. A system as defined in claim 1 wherein said hydraulic circuit meansincludes a solenoid control valve which permits fluid to flow in onlyone direction when said solenoid is deenergized and which permits fluidto flow in the other direction when said solenoid is energizcd.

4. A system as defined in claim 1 wherein a pneumatichydraulictransducer interconnects said pneumatic circuit means to said hydrauliccircuit means.

5. A system as defined in claim 1 wherein said pneumatic circuit meansincludes a solenoid valve for connecting said source of pressure to saidpneumatic circuit means when said solenoid is deenergized and fordisconnecting said source of pressure from said pneumatic circuit meanswhen said solenoid is energized.

6. A system as defined in claim 1 wherein said source of pressureincludes a pneumatic compressor and reser- Volt.

7. A control system for car retarders comprising a plurality of firstfluid means each having at least one ram cooperatively associated withthe car retarder and a directional control valve for regulating the flowof fluid to and from said ram, and at least one second fluid meansinterconnected to said plurality of first fluid means and including asource of pressure for causing the car retarder to assume a firstposition when the fluid of said first fluid means flows to said ram andfor enabling the car retarder to assume a second position when the fluidof said fluid means flows from said ram.

8. A control system as defined in claim 7 wherein said first fluid meanscomprises a hydraulic system and said second fluid means comprises apneumatic system.

9. A control system as defined in claim 7 wherein a transducerinterconnects said second fluid means to said plurality of first fluidmeans.

10. A control system as defined in claim 7 wherein a plurality oftransducers interconnect said second fluid means to said plurality offirst fluid means.

11. A control system as defined in claim 7 wherein said directionalcontrol valve comprises an electric solenoid valve which permits theflow of fluid to said ram when said solenoid is dcenergized and whichpermits the flow of fluid from said ram when said solenoid is energized.

12. A control system as defined in claim 7 wherein said source ofpressure includes a compressor and a for cutting-off said source ofpressure when said solenoid is deenergized.

14. A pneumatically-powered hydraulically-actuatedelectrically-controlled system for a weight proportional car retardercomprising: a source of pneumatic pressure including a compressor and areservoir, a first solenoid control valve pneumatically coupled to saidreservoir, a plurality of pneumatic-hydraulic transducers pneumaticallycoupled to said first solenoid control valve, a plurality of secondsolenoid control valves hydraulically coupled to separate ones of saidplurality of pneumatichydraulic transducers, and a plurality ofhydraulic rams hydraulically coupled to separate ones of said pluralityof second solenoid control valves and mechanic-ally connected to the carretarder for rendering and maintaining the car retarder in its brakingposition when said first and sec-0nd solenoid control valves aredeenergized and for rendering and sustaining the car retarder in itsnon-braking position when said first and second solenoid control valvesare energized.

15. A pneumatically-powered hydraulically-actuatedelectrically-controlled system for a weight proportional car retardercomprising: a source of pneumatic pressure including a compressor and areservoir, a first solenoid valve pneumatically coupled to saidreservoir, a pneumatic-hydraulic transducer pneumatically coupled tosaid first solenoid control valve, a plurality of second solenoidcontrol valves hydraulically coupled to said pneumatichydraul-ictransducer, and a plurality of hydraulic rams hydraulically coupled toseparate ones of said plurality of second solenoid control valves andmechanically connected to the car retarder for rendering and maintainingthe car retarder in its braking position when said first and secondsolenoid control valves are deenergized and for rendering and sustainingthe car retarder in its non-braking position when said first and secondsolenoid control valves are energized.

References Cited UNITED STATES PATENTS 3,200,245 8/1965 Brown 188-62 X3,209,865 10/1965 Wynn 188-62 3,227,246 1/ 1966 Wilson 18862 DUANE A.REGER, Primary Examiner.

1. A SYSTEM FOR CONTROLLING THE POSITION OF A CAR RETARDER COMPRISING:HYDRAULIC ACTUATING MEANS COOPERATIVELY ASSOCIATED WITH THE CARRETARDER, HYDRAULIC CIRCUIT MEANS FLUIDLY COUPLED TO SAID HYDRAULICACTUATING MEANS, AND PNEUMATIC CIRCUIT MEANS INTERCONNECTED TO SAIDHYDRAULIC CIRCUIT MEANS AND HAVING A SOURCE OF PRESSURE FOR CAUSING THECAR RETARDER TO ASSUME A FIRST POSITION WHEN